The invention relates generally to a fiber optic hydrophone that is acceleration-insensitive and is adaptable for use in noisy environments. The invention relates particularly to a fiber optic hydrophone having a rigid mandrel and compliant backed cavities to provide enhanced acoustic sensitivity.
The conventional method for underwater sound detection employs piezoelectric transducers, along with associated electronics. Because conventional sensors are electrically active, it is required that power be supplied to the sensors underwater, which causes additional weight, complexity, and cost. Further, conventional systems have low reliability because seals in the underwater hydrophones may leak and cause equipment malfunctions. In addition, conventional sensor have limited sensitivities and are susceptible to electromagnetic pickup.
Fiber optic hydrophones are disclosed in U.S. Pat. Nos. 4,525,818 and 4,570,248. The size of prior art fiber optic hydrophones has limited the directional response has been limited to low frequencies.